Are they? What's the current status of their retirement accounts? What are their plans for funding their kids' educations? Do they own their own homes?
There's a difference between being able to survive and living a good life. The reason the more financially literate and educated people put off having kids is because they care about their own futures and the futures of their kids. They know they can't work forever and they know that the current political environment is one of removing and undoing every single social safety net out there. Meaning, a mistake today very well could mean homelessness/eating cat food/etc or ultimately starving to death.
My father-in-law is 72 and still needs to work to pay the bills. He can't retire. That's the future for the less financially and intellectually equipped parents and their kids in the current political climate.
That doesn't change the reality of self-interest.
If someone is struggling to take care of themselves, why would they have children? Heck, if you have people working 80+ hours a week just to stay housed, when can they find time to have kids?
Cruel societies punish people for having kids. We have a cruel society. The 90s "welfare queen" talk caused the US federal and state governments to gut social programs specifically designed to aid and support people in having families.
For so many people, affording the necessities requires 2 incomes. Childcare either takes out an income or it incurs a huge new necessity.
And then there's always the impact of "what if the child has a disability" in that case most people are really truly screwed in the US if that happens.
Well, yes. Because they've not quite got the heavily broadcast message that having children is a bad financial decision. The West is a society that respects wealth and has a vague distaste for children and parents.
The UK has an ongoing debate about the two-child limit on child benefit payments. Whenever this is discussed, furious people appear out of the woodwork to condemn those who dare to have three children as financially irresponsible.
An additional child at £17.25 a week is an intolerable cost to the taxpayer, apparently. And you wonder why people don't have more children.
In addition and in general, paying people to have kids is not a good solution. More often than not, it leads to less educated, less capable people becoming baby mills and ruining the rest of society with their poorly raised children. 2 children is fine. It's almost replacement level.